**2.5 Non-Newtonian fluids**

Non-Newtonian fluids do not show a linear relationship between shear stress and shear rate. This is due to the complex structure and deformation effects exhibited by the materials involved in such fluids. The non-Newtonian fluids are however diverse and can be characterised as e.g. pseudoplastic, viscoplastic, dilatant and thixotropic fluids (Schramm, 2000).
